The Internet Protocol (IP) Multimedia Subsystem (IMS) delivers IP multimedia services to access terminals. IMS utilizes call session control functions (CSCFs) to provide the services. CSCFs are Session Initiation Protocol (SIP) servers and proxies that process SIP signaling packets. A proxy-CSCF (P-CSCF) is a SIP proxy that is typically the first point of contact for an access terminal. A serving-CSCF (S-CSCF) is a SIP server that performs session control. The serving-CSCF operates as a home proxy for an access terminal and manages the features and communication sessions for the terminal. An interrogating-CSCF (I-CSCF) is a SIP proxy that may be used as a forwarding point for SIP packets.
A serving-CSCF is assigned to an access terminal. The incoming and outgoing sessions for the access terminal pass through the assigned serving-CSCF. Known techniques for assigning the serving-CSCF, however, may not be efficient in certain situations.